Alpha-Data Copy Bank USB 2.0 hard drive case

The difference between Alpha-Data's Copy Bank 2.5-inch hard drive enclosure with USB 2.0 support and any other enclosure is that the Alpha-Data can be powered by 4 AA batteries so it can directly connect to digital cameras and media players for file copying without the need for a PC—or a power outlet.
Available next month in Japan for about $60, the Copy Bank can support hard drives up to 80GB (you supply your own, it
is just an enclosure, holmes), but no mention of how much runtime it gets running off of batteries is mentioned, which worries us a bit as we wouldn't want to lose all our C&C Music Factory MP3 files because our batteries died.